1. Field of the Invention
The invention relates generally to devices that propel forcibly into the air spherical objects such as tennis balls or the like for practice or training purposes. In a more particular sense, the invention relates to means for imparting oscillatory motion to the discharge barrel of a propulsion device of the type stated about an axis that, if not completely vertical, has at least a vertical component. The invention is directed to a programming-type improvement in the means for creating oscillating motion of the discharge barrel whereby to time the oscillation and the extent of angular travel thereof in relation to the successive discharge of the balls during the normal rotation of the distributor or feed magazine.
2. Description of the Prior Art
Tennis ball propulsion devices, for use as training aids, are of course very well known. A typical propulsion device of the type stated may be seen in U.S. Pat. No. 4,027,646 issued June 7, 1977. In such devices, there is a hopper, a rotary feed magazine or distributor having a plurality of angularly spaced ball-receiving openings or sleeves, and a conduit that extends from the distributor location to the outlet of the device. Passage of a ball from the distributor through said conduit occurs within a pressurizing chamber, in such fashion that the balls are successively fed through the conduit. Pressure is built up behind each of them, until the pressure reaches a value such as to cause the ball to be forcibly discharged.
In the prior art, various means have heretofore been devised for changing or varying the path in which the successively propelled objects will be directed. It is known, for example, to cause the discharge barrel of such a device to be oscillated, that is, moved in a continuous back-and-forth or side-to-side motion, so that the user will be required to run back-and-forth across the tennis court, to return each ball, thereby to obtain practice in executing forehand as well as backhand strokes, increase his or her stamina, and otherwise obtain added benefits from the use of the propulsion device. See for example, Sweeton et al U.S. Pat. No. 4,006,726 issued to the assignee of the present application, and the patents cited therein.
The prior art devices have been effective in respect to achieving the broad objects of varying the paths along which the tennis balls or other spherical objects are discharged. However, the prior art has had certain disadvantages, including, for example, the provision of oscillatory motion only through the medium of expensive electrical, electronic, or complex mechanical devices.
Further, in the prior art such devices have in many instances been required to be built into the complete device, in such fashion that the user would be prevented from manufacturing, with the same components, both standard and programmed oscillating type discharge mechanisms.
In still other prior art devices, it has not been possible for a user to adjust, with maximum speed and ease, the width of the oscillating path in which the discharge end of the barrel is to travel. And in yet other cases the user is prevented from disengaging the oscillating mechanism except with considerable difficulty.
Thus, the prior art has broadly suggested the concept of timing oscillation of a discharge barrel in relation to the feeding of balls into the propulsion device, but heretofore, so far as is known, the prior art has not suggested a mechanical linkage between the ball feeding and the discharge mechanisms, such as to optionally connect or disconnect the oscillation-producing means, adjust swiftly and easily the extent of oscillating travel in relation to the quantum and frequency of ball delivery, and, in general, facilitate the manufacture of propulsion devices of this type so as to incorporate an oscillating mechanism that is inexpensive, simple, and trouble free, and that can be either incorporated in or left out of the propulsion device, according to the desires of the manufacturer and without changing in either instance the design or assembly of the basic propulsion device.